There is no single source to find music manuscripts of world. The major sources are:
- RISM A/II (Music Manuscript from 1600-1850): Online catalog of music manuscripts
- Census-Catalogue of Manuscript Sources of Polyphonic Music, 1400-1550: 5 printed volumes of ms. (ML135 .C46 v. 1-5, Music Reference)
- RISM B/IV (Music Manuscripts from 11th to 16th Centuries): Printed catalog in 5 parts. (ML113 .I6 Ser. B v. 4, pt. 1-5 and suppl.)
- New Grove Dictionary of Music and Musicians -- the article "Sources. Ms." This article includes a list of music manuscripts from the 9th century until the Renaissance, arranged by chronological periods and then alphabetically by cities. REF Is. ML100 .N48 2001 v. 23 or online
A few terms pertaining to manuscripts:
What is a manuscript? A Hand-written document (manu=hand; script=writing).
Autographed manuscript: A signed hand-written document; the signature is not necessarily the author's. For example, it can be a copyist's signature.
Holograph manuscript: A manuscript in the author's or composer's hand.
Archives (Archival Collection): A collection of manuscripts generated by one person or an institution. It can include music scores, audio recordings, letters, diaries, or printed scores with performer's markings, etc.
Pagination: Manuscripts sometimes use the term "folio," meaning a leave, rather than a "page." Thus, the numbering will be on every other page, beginning on the recto, the right hand side page of an open volume. For example, the first right hand side will be 1r (1 recto), and the next page, on the back side of that leaf, is called 1v (1 verso), literally, the reverse side of the page.
Custos (direct or guida): A sign (that resembles a check mark or a mordent) that is placed at the end of a music manuscript staff line, indicating the first pitch of the next line. The first use of this dates back to the 11th century, and the practice continues into the 18th century.
Illuminated manuscript: It refers to manuscripts with gold-leaved letters or images. The first letter of text in music manuscripts is often ornamented and sometimes burnished with gold leaf.
Most of these links will allow access to music and other manuscripts. Music Manuscripts link will be thus specified:
Cecilia Project -- Finding music collections (archives included) in the UK http://www.cecilia-uk.org/
British Library Manuscript Catalogue -- http://molcat.bl.uk
Italian National Manuscripts -- http://www.braidense.it/urfm/)
National Union Catalogue of Manuscripts (NUCMC) -- http://www.loc.gov/coll/nucmc/
RISM B/IV (Manuscripts of Polyphonic Music, 11th - 16th Cenuturies): Includes entries of all known polyphonic manuscripts beginning in the Ars Nova period. Each piece is cataloged with an incipit and description. (Music Ref ML113 .I6 Ser. B v. 4, pts. 1-5, and suppl.)
Census-Catalogue of manuscript sources of polyphonic music, 1400-1550 : Includes entries for all known manuscript sources of polyphonic music in mensural notation for the period 1400-1550; arranged alphabetically. (Music Ref ML135.C46 v.1-5)
RISM B/III: The Theory of Music. Manuscripts of music theory treatises from the Carolingian Era up to 1400. Arranged geographically. Ref Is. M113 .I6 Ser. B v. 3, pts. 1-6